I agree with Tommy's statement. They are Damsels, and with any damselfish you are taking a chance. I had a group of 3 chromis as well, and luckily they only went after each other, and not other fish, but eventually the biggest one was the only guy left, so I decided to be done with any damsels in my tank.
55 gallon reef tank. AquaticLife 4-bulb T5 HO with 4 LED moonlights. Reef Octopus BH-1000 HOB protein skimmer. TLF Phosban Reactor 150 running 400ml of NPX Bioplastics with a Maxi-Jet 1100 and a BRS Reactor running activated carbon with a Maxi-Jet 900. Vortech MP10w.